Reactivating platinum catalyst



ihiitiiisi ii Patented Der-e. ti,

' This is due,'usually, to the state of the platinum com-- ponent, which has not been reverted to the original state,

2 9 M v and, which may have, in fact, been adversely affected by v v the oxidation procedure for the removai of the carbona REACTIVATING PLATINUM CATALYST 5 ceous materiai.

. I 5 Also, regeneration by burning in an oxygen-containing gfiggfifi gfig hxgsgggf gglkh izg ag g gg yfiz gas quite often produces substances which are, in and of themselves, inherently detrimental to catalyst activity For example, the oxidation of carbonaceous material produces carbon monoxide which is widely known to a substance having a deactivating action on metal-coir taining catalysts, being particularly deleterious to platinum-containing composites. Usually, the catalyst will, after regeneration, function. The present application is a continuation-in-part of my acceptably for a period of time shorter than that expert co-pending application, Serial No. 595,863, filed July 5, enced with the fresh catalyst. This, of course, necessitates Plaines, ililh, a corporation or Delaware c Wiimwtaet ieaiuayz9,'1958,set-.Ne.rss,sss n a nan. (or. 252-416) e 1956, now abandoned, This invention relates to the a second regeneration which again produces a catalyst reactivation of platinum-containing catalytic composites, less desirable than the catalyst before regeneration. Each and is specifically directed toward the reactivation of successive regeneration results in a catalyst which enplatinutn containing catalytic. jcomposites through the Q hibits a shorter period of acceptable activity than that er. utillaatiohof particular oxides of nitrogen. r hibited after the preceding regeneration. Eventually, it lPatinum-containing catalytic composites have attained becomes necessary to replace completely the catalyst. extensive commercial utility. Industries such as the pharfurther regeneration not being econo'mically feasible. maceuticaL'dctergent, petroleum, insecticidal, etc., utilize The object of the present invention is to-provide platinumcontaining catalysts to promote a multitude of 5 method, for the reactivation of a patinum-containing reactions among which are hydrogenation, cyclization, catalyst, which reconstitutes the platinum component, and cracking, polymerization, dehydrogenation, dehydrocycliwhich will produce a reactivated catalyst having a high. zation, sultonation, oxidation and, to a certain minor ex-- degree of activity and possessing the capability to func= tent, hydrocracking and isomcrization. v tion acceptably for an extended period of time. Another 'Whatever the "industry and reaction, it is extremely object is to-provide a method for reactivating a platinum essential, forcommercial acceptability, that the platinum containing catalyst which will not resultin the removai. catalyst exhibits a prolonged capability to perform its inof the platinum component from the other components tendedifunction, aswellflas a high degree of activity in employed in the catalyst. promoting the desired reaction or combination of reacin one embodiment, the present invention relates to a tions; method for reactivating a deactivated platinum compo- After extended periods of use,- platinum catalysts neat-refractory inorganic oxide catalyst which comprises usually become deactivated and thereby lose their capatreating said deactivated catalyst in the presence of halo-- bility to perform asdesired. Deactivation-of the catalyst 7 gen with an oxidcof nitrogen selected from the group is seldom sudden; most often, deactivation occurs through consisting of N 0 N0 N 0 and mixtures thereof. a gradual decline in activityuntil such time as the catalyst 40 In another embodiment, the present invention relates is no longer act'ive to the necessary and desired degree. to a method for reactivating a deactivated platinum corn- Catalyst deactivation may result from any one or a component-refractory oxide catalyst which comprises oxidizhination of adverse effects. These effects may, in turn. ing said deactivated catalyst in air and thereafter, in the result from substances which are peculiar toa particular presence of halogen, treating said air-oxidized catalyst catalyst, and which either give rise to a change in they i with an oxide of nitrogen selected from the group con physical state of the components of the catalyst, or result sisting of N 0 N0 N 0 and mixtures thereof.

. in a loss of said components. Deactivationmay also re- Ina specific embodiment, the present invention relates suit from the deposition of impurities: theseimpurities to a method for reactivating a deactivated platinumusually take the form of solids which cover the catalytialumina-chloride catalyst whichcomprises oxidizing said cally active centers and surfaces, and shield them from catalyst in air at a temperature of from about 300 C. the materials being processed. Quite often'gcatalyst de-. to about 700 (3., treating the air-oxidized'catalyst witl'i activation is effected simply as a result of an extended an-oxide of nitrogen selected from the" group consisting period of use: as such, thedeactivation generally involves of N 0 N0 N 0 and mixtures thereof at a tempera- .a' change in the" state of the metal component. This ture in excess of 25 6., removing said oxide of nitrog '1 change is usually an increase in crystallite size, a change and thereafter subjecting said catalyst to a reducing treatint-oxidation state and/or a change in regard to the assoment with: hydrogen at a temperature in excess of 25 ciatioii'oi the metal component withother catalytic com-. The method of the present invention affords benefits, ponents. I v A heretofore not obtained, to processes for the reactivation. The deposition of coke, orother carbonaceousmaof platinum-containing catalytic composites; it is not in terial, is either'adirect cause of catalyst deactivation, or tended to limit unduly the present invention to those exists in conjunction with any of vthe aforementioned catalysts comprising platinum as the sole catalyticaiiy causes of deactivation. A widely utilized. method, active metallic component. Other-metals may be comthought to regenerate a catalyst effectively, which catalyst bined with the platinum, particularly metals of the noble hasbeen deactivated by the deposition'of carbonaceous metal family, and include rhodium, ruthenium, tungsten. material and/or any of the hereinbcfore causes of deac silver, palladium, titanium, hafnium, gold, rhenium tivation, is to subject the catalyst to burning in an oxygen mixtures of two or more,' It is understood that the t often less thanthe activity of the catalyst prior to use, metals hereinabove set forth, it is generally compo,

containing gas, usually air, at'elevated temperatures. It etallic components, or mixtures thereof, may exist is well ltnown that this method removes etfectively the the elemental state, 0: in some combined form as the. carbonaceous" material, and to all, visual appearances, oxide, halide, sulfate, nitrate, etc.

produces an activecatalyst. However, the degree o Whatever the metal component, whether platinum, activity or the catalyst regenerated in this manner, is quite or a combination of platinum and one or more of the accuses with a highly refractory inorganic oxide such as alumina, silica, zircouia, silica-alumina, silica-zirconia, silicaaluminazirconia, silica-thoria, silica-alumina-thoria, aluniina magnesia, silica-alumina-magnesia, etc. Due to its excellent stahdity characteristics at high temperatures, alumina or alumina-silica is preferred as the carrier material for the other components of the catalyst. ltis understood that these refractory inorganic oxides may be made in any suitable manner including separate, sucplatinum, subsequently commingling this mixture with the alumina. The resulting mixture is then dried at a temperature of from about 200 C. to about 700 C. for a period of from about 2 hours to about 24 hours or more, and is subsequently formed into any desired shape such as pills, powder, or granules, if said alumina is not already in the desired shape. Regardless of the identity of the metal component and refractory inorganic oxide, or the forms thereof, it is understood that the ultimate composite may be made in any suitable manner including separate, successive, or co-precipitation methods of manufacture.

Whatever the method of manufacture, the catalyst so produced, and ultimately deactivated in use, may be reactivated by the process of the present invention. As

hereinbefore set forth, the present invention proposes a.

method for 'reactivating a deactivated platinum-containing catalyst through specific treatments with N N0 N 0 and mixtures thereof. The method will yield a catalyst having a high degree of activity, and increase, thereby, the length of time in which the catalyst is capable of performing as desired.

It is preferred to subject the deactivated catalyst to air oxidation prior tothe treatment with one of the here.- inbefore stated oxides of nitrogen. Oxidation in an atmosphere of air will remove substantially completely the carbonaceous material deposited upon the catalyst, thereby enhancing the apparent action of the oxide of nitrogen on the metallic component. .The pre-oxidation treatment may employ any suitable free oxygen containing gaseous material; air is preferred because of its natural abundance, and the economical feasibility of its utilization. Preoxidation with air, or any other suitable free-oxygen containing gaseous substance, need not necessarily precede the treatment with one of the aforementioned oxides of nitrogen in those instances where the deactivated catalyst is virtually void of coke and other carbonaceous-material. In any case, the method of the present invention will reactivate adeactivated catalyst, and yield a catalyst having a high degree of activity, and an extended period of utility.

It is understood that the oxides of nitrogen may or may not be employed per so. They may be utilized as mixtures comprising two or more, such as N0 and.

N 0 N 0 and N 0 (which is an equilibrium form of N0 etc. Said oxides of nitrogen may hc'admixed with various diluents such as, but not limited to,-'air, nitrogen, other inert gases, etc., and as hereinbefore stated, halogen is present. The presence of water is controlled, minor amounts, also appears to be beneficial. Said oxides of nitrogen may result hrom other compounds and mixtures which either yield the same at reaction conditions, or form them in situ.

The essential feature of the present invention is the presenceof halogen during the treatment with the oxide of nitrogen, and such halogen may be a componen.

the catalyst to he reactivated or may be admixed with particular oxide of nitrogen employed. The use oi chlorine and/or bromine is preferred, although fluorine and iodine may be utihzed. Any suitable concentration of halogen, from an amount which yields a marked improvement, to an amount which is uneconomically excess, may be used. However, it is preferred that said halogen be present in excess of 0.1 percent by Weight of the refractory oxide. It is understood that, although the use of any of these halogens will increase the ac resulting from reactivation, the various halogens are not equivalent, and different halogens may be used with different catalysts.

In accordance with the present invention, the halogen may be added in any suitable manner. Said added halogen may he in the elemental state as chlorine gas, or existing as a combined halide such as, but not limited to, HCl, CCl and alkyl halides such as ethyl chloride, propyl chloride, methyl chloride, butyl chloride, etc. As hereinabove set forth in a specific embodiment, said halogen may be a component of the catalyst which is to he reactivated. It is further understood that said halogen may comprise mixtures of two or more of the halides, whether as components of the catalyst, or as halogen which is to be added.

To further improve the activity of the catalyst, it is desirable to subject said catalyst to a reducing treatment.

Prionto said reducing treatment, it is necessary that the catalyst is stripped of the oxide of nitrogen by being subjected to a sweeping treatment. The sweeping or stripping agent may be any gaseous substance not having a reducing action on said oxide of nitrogen. Suitable sweeping agents include air, nitrogen, carbon dioxide, mixtures of the same, etc. It is essential that said reducing treatment is not effected in the presence of the oxide of nitrogen. Nitric oxide (NO), although an oxide of nitrogen, is excluded due to its reducing action. Nitrous oxide (N 0) has been found to be incapable of reconstituting the metallic component.

The preferred method of reactivating a deactivated catalyst comprising a platinum metal component coma posited with a refractory oxide such as, for example, a platinum-alumina-choride catalyst, is to subject said catalyst to air oxidation at a temperature of from about 300 C. to about 700 C., and further to subject said catalyst, at a temperature in excess of 25 C. with an upper limit of from about 800 C. to about 1000" Q, to the action of an oxide of nitrogen selected fiom group consisting of N 0 N0 N 0 and mixtures there following .this latter treatment by sweeping the camps te with air to remove traces of the oxide of nitrogen, out removing the platinum component, and subjecting the catalyst to a. reducing treatment wiui fag drogen at a temperature in excess oil? C. with upper limit of from about 800 C. to about NEW C. The preferred method employs a. temperature of from about 300" C. to about 700 C. for the oxidation, oxide of nitrogen, sweeping, and reducing treatments. The reducing treatment may be omitted in those instances where, as a normally integral part of the process in which the catalyst is intended for use, said catalyst is fimt anhiected to the action of a suitable reducing agent. It is further understood that the method of this invention may employ either downflovl, upflow, or crossfiow in a closed vessel, or countercurrent or concurrent flow through a fixed, fluidized, or continuously moving bed of catalyst. -.The following examples are introduced to fluther illustrate the utility of the-present invention and are not intended to limit the some to the specific materials and conditions involved.

nunbers .are, therefore, highly significant.

' hour. i

EXAMPLE! Analu mina carrier material wasprepared from a mixture of equal volumes of a.28% by weight solution of hexamethylene tetramine in water, and an aluminum chloride ,hydrosol'containing 12% by weight aluminum and 10.8% by weight chloride. The mixture was formed into spheres, by the oil-drop. method, and were washed,

dried to atemperature of 650C. and then calcined at 130 grams of the calcined spheres were soaked in 229 millilitersof a water solution of 99 milliliters off-chloroplatinic acid containing 9.92 milligrams of platinum per milliliter.

- The spheres were then dried at a temperature of 100 C., and oxidized at a temperature of 500 C. The reas a standard, was sllbiecte'dto an activity test which consisted of reducing the catalyst in hydrogen at 500 C. and atmospheric pressure, and passing normal heptane over said first catalyst portion at a temperature of 325 C., atmospheric pressure, a liquid hourly space velocity of 2.4 (liquid hourly space velocity is defined as the volume of liquid charged per hour per volume or catalyst within the reaction zone), and in an atmosphere of hydrogen equivalent to-an 8:1 molal ratio of hydrogen to normal heptane. 'The volume percent conversion of normal heptane to toluene under the above conditions is indicative of the activity of-the catalyst. The abovedescribed activity test was selected intentionally because of its severity, and small improvements in small 7 A second portion of the; platinum-alumina-chloride catalyst was placed in a furnace tube and brought to a temperature of 500 C. The catalyst was then subjected to-the action of a stream of carbon monoxide for a period of one -It' hasbeen shown that the use of carbon monoxide as'acatalyst deactivator is effective. in producing effects which are similar to those experienced by a catalyst which has been deactivated-through normal use. Quite often, the carbon monoxide treatment is more severe,

degree. r 5 The furnace tube was cooled and the catalyst therein I removed. A portion of the catalyst which was deactivat'ed by carbon monoxide was subjected to the normal hept'z a'ne activity testas hereinbefore defined. A second ature of 500 C, A stream of air was passed through the furnace tube" at a temperature of 500 C. for a period of about one hour. This was followed by a stream of N0 at a rate of'50 cc. per minute for a period of about crystallite size, and the carbon monoxide adsorption data are showninthe following table:

1 TABLE 1 Without Deactivated With N0, H Treatment with 00 Treatment Toluene Yield, v01. Percent; 2. e 0. 015 2. s crystallite Size A-.--. 20 27 C0 Adsorption, Moles CO/ M01. Pt '0. 75 0. 05 0.8a

sorption analysis are indicative of the relative size oi metal component crystallites, and the availability of active centers and surfaces for catalysis, and have been found, therefore, to be a good measure of catalyst activ- 'ity. High carbon monoxide adsorptivity, and small crystallite size tend to indicate high catalytic activity.

The results'of the activity tests, the determinations of.

In addition, a distinct color change was observed between .the carbon monoxide-deactivated catalyst and the NO treated portion. ,The carbon monoxide-deacti-.

I vated catalyst, after the air-oxidation treatment, exhibited and yields a catalyst which is deactivated to a still greater EXAMPLE n A sample of. the platinum-alumina-chloride catalyst made as described in Example I, was soaked ina solue tion. of ammonium nitrate: this treatment with ammonium nitrate, serves to effectively remove the chloride from the catalyst. The catalyst sample was then sub jected to the deactivating action of carbon monoxide as hereinbefore described in Example I.

A first portion of the carbon monoxide-deactivated catalyst was subjected to the action of N0 by the method of the present invention. Said first catalyst por-' tion was then subjected'to the normal heptane activity test as defined in Example I, which test indicated a 1.7 volume percent yield of toluene. This in itself is a substantial improvement over the toluene yield of the carbon monoxide-deactivated catalyst as indicated in Table i I, that of 0.015 volume percent.

A second portion of the carbon monoxide-deactivated catalyst was soaked in an aqueous solution of ammonium chloride: this treatment with ammonium chloride serves to re-deposit the chloride onto the catalyst.

5 minutes, and further followed by a stream'of air at a;

temperatureof'500 C. for a period of one hour to remove'traces of N0 'The catalystwas 'thensubjected to a'reducing treatment at a temperature of 500 C.- in

a streamof hydrogen for a period of one hour. The furnace tube was" then cooled, the catalyst removed and then subjected to the test for activity as hereinbefore defined. a

The results of the activity'testsclearly illustrate the benefits derived from employing the present invention.

In addition to the-activity tests, the untreated, the carbon monoxide-deactivated, and the NO -treated portions of the platinum alumina-chloride catalyst were analyzed by X-ray diffraction to determine the crystallite size of the metal component Also, said portions of catalyst were subjected to an analysis to determine the quantity of carbon monoxide adsorbed under a standard set of-con'di Said second catalyst portion was then subjected to the action of N0 by the method of the present invention. After the N0 treatment, the catalyst was subjected to the normal hept'ane activity test as hereinbefore defined. There resulted a tolueneyield of 2.8 volume percent which is significantly greater than that yielded by the chloride-free, first deactivated catalyst portion.

I EXAMPLE III A platinum-alumina-chloride catalyst prepared as hereinbefore described in Example I is deactivated by car- .ofany suitable inert gas such as nitrogen, is passed throughthe container and then into the furnace tube carrying vaporized N 0 with it. 'The catalyst is further subjected to a stream of air at a temperature of 500 C;

to remove traces of N 05, and thereafter, further subjected to a stream of hydrogen, at a temperature of 500 C. for a period of one hour.

The furnace tube is cooled, and the reactivated catalyst therein is removed. A distinct color change is observed, said color change being indicative of a more active state of the metal component. The catalyst is then subjected to the normal heptane activity test as defined in Example I, the result of which furthersubstantiates the existence of a more active state of the metal component, and, therefore, a more active catalyst composite.

EXAMPLE IV A platinum-aluminum-chloride catalyst, prepared as hereinbefore described in Example I, is placed in a furnace tube and brought to a temperature of 500 C. The catalyst'is then subjected to a stream of carbon mbnoxide which, as hercinbefore stated, deactivates effectively said catalyst. The deactivated catalyst is then subjected to the method of this invention through the action of N 0 introduced into the furnace tube by passing the stream of any suitable inert gas, such as nitrogen, first through a vessel containing arsenic oxide and nitric acid, the reaction of which produces N 0 and then into said furnace tube. After a period of about 5 minutes, a stream of air at a temperature of 500 C. is passed through the tube for a period of one hour to remove all traces of N 0 Thereafter, said catalyst'is subjected to a'stream of hydrogen at a temperature of 500 C. for a period of one hour.

The furnace tube is cooled; the reactivated catalyst is removed, and subjected to the activity test as hereinbefore defined in Example I. The results of the activity test show the catalyst to be reactivated, and substantiate the existence of a more active state of the metal component.

The foregoing examples and specification clearly illustrate the several embodiments of the present invention and the benefits afforded the reactivation of a platinumcontaining catalyticcomposite through the utilization thereof.

I claim as my invention:

1. A method for reactivating a deactivated platinumcontaining refractory oxide catalyst "which comprises 8 oxidizing said deactivated catalyst in air at a temperature of from about 300? C. to about 700 C., thereafter treating the air-oxidized catalyst, at a temperature of from about 25 C. to about 1000 C. in the presence of halogen in excess of 0.1% by weight, with an oxide of nitrogen selected from the group consisting of N 0 N0 N 0 and mixtures thereof, stripping said oxide of nitrogen from said platinum-containing catalyst with a gas not having a reducing action on said oxide of nitrogen, and thereafter subjecting said catalyst to a reducing treatment with hydrogen at a temperature of from about.

25 C. to about l000 C.

2. The method of claiml further characterized in that said oxidizing agent comprises N 0 3. The method of claim 1 further characterized in that said oxidizing agent comprises N0 4. The 'method of claim 1 further characterized in that said oxidizing agent comprises N 0 5. The method of claim 1 further characterized in that said refractory oxide comprises alumina.

6. The method of claim 1 further characterized in that said halogen comprises chlorine.

7. The method of claim 1 further characterized in that said halogen comprises bromine.

8. A method for reactivating a deactivated platinumalumina-chloride catalyst which comprises oxidizing said deactivated catalyst in airat a temperature of from about 300 C. to about 700 C., thereafter treating the air-oxidized catalyst, at a temperature of from about 25 C. to about 1000 C., with an oxide of nitrogen selected from the group consisting of N 0 N0 and N 0 removing'said oxide of nitrogen by sweeping with air, without removing said platinum, and thereafter subjecting said catalyst to a reducing treatment with hydrogen at a temperature of from about 25 C. to about 1000 C.

References Cited in the file of this patent UNITED STATES PATENTS 1,678,627 Iaeger July 24, 1928 2,381,659 Frey Aug. 7, 1945 FOREIGN PATENTS 744,429 Great Britain Feb. 8, 1956 

1. A METHOD FOR REACTIVATING A DEACTIVATED PLATINUMCONTAINING REFACTORY OXIDE CATALYST WITH COMPRISES OXIDIZING SAID DEACTIVATED CATALYST IN AIR AT A TEMPERATURE OF FROM ABOUT 3000*C. TO ABOUT 7000*C., THEREAFTER TREATING THE AIR-OXIDIZED CATALYST AT A TEMPERATURE OF FROM ABOUT 28*C. TO 1000*C. IN THE PRESENCE OF HALOGEN IN EXCESS OD 0.1% BY WEIGHT, WITH AN OXIDE OF NITROGEN SELECTED FROM THE GROUP CONSISTING OF N2O3, NO2, N2O5 AND MIXTURES THEREOF, STRIPPING SAID OXIDE OF NITROGEN FROM SAID PLATINUM-CONTAINING CATALYST WITH A GAS NOT HAVING A REDUCING ACTION ON SAID OXIDE OF NITROGEN, AND THEREAFTER SUBJECTING SAID CATALYST TO A REDUCING TREATMENT WITH HYDROGEN AT A TEMPERATURE OF FROM ABOUT 25*C. TO ABOUT 1000*C.
 8. A METHOD FOR REACATIVING A DEACTIVATED PLATINUMALUMINA-CHLORIDE CATALYST WHICH COMPRISES OXIDIZING SAID DEACTIVATED CATALYST IN AIR AT A TEMPERATURE OF FROM ABOUT 3000*C. TO ABOUT 7000*C., THEREAFTER THREATING THE AIR-OXIDIZED CATALYST, AT A TEMPERATURE OF FROM ABOUT 25* C. TO ABOUT 1000*C., WITH AN OXIDE OF NITROGEN SELECTED FROM THE GROUP CONSISTING OC N2O3, NO2, AND N2O5, REMOVING SAID OXIDE OF NITROGEN BY SWEEPING WITH AIR, WITHOUT REMOVING SAID PLATINUM, AND THEREAFTER SUBJECTING SAID CATALYST TO A REDUCING TREATMENT WITH HYDROGEN AT A TEMPERATURE OF FROM ABOUT 25*C. TO ABOUT 1000*C. 